Let's Make Robots!

Noisy LM386 based audio amplifier

Inspired by this post from Salvage, I ordered a couple of gameDR Smack Talk for the XBOX units. The volume is way too low to drive a speaker directly, so I need an audio amplifier.

That led me to this post from Calculon320 on building an amplifier with an LM386. I breadboarded the audio amp, and it definitely amplified. However it also added a lot of noise. It could be cleaning it all up on a perf board would fix some of that, but it is very noticable.

Practical question about servos and capacitors

I have read in many places on this site about using capacitors to reduce motor and servo noise. I am now using 0.1 uF capacitors across the leads of my motors as standard practice. I'm also using 470 uF and 0.1 uF capacitors around both sides of my voltage regulator. As yet I haven't tried applying a cap to a servo, and I have a quick question.

SRF05 with common in/out pin

I'm trying to get the PICAXE-28x1 to work with the SRF05 usnig a common input and output pin. The reason is I want to conserve my input and output pins. I've seen discussions on this site about it, but I don't know if anyone ever succeded.

Since the 28x1 allows you to reconfigure digital inputs as digital outputs, I figured it should be possible to use "Mode 2" of the SRF05 with a commmon single input and output.

Here's the code I tried. I also tried some varations the timing, as noted.  No luck so far.

Using Google search for LMR

Since we've been getting inconsistent results from the LMR search engine, I've taken to using Google search, and specifying the site.

In case you don't know how to do this, just go to Google and search for:

site:letsmakerobots.com <whatever you are looking for>

For example, if you want to find all references to Mr Basic, you type:

site:letsmakerobots.com "Mr Basic"


360 Range Finder

I just received my SRF05 and I can't wait to start using it.  While I was thinking about it, it occurred to me that I always see the SRF05 mounted on a servo, which allows maybe a 180 degree field of view for a robot. I wondered if anyone ever mounted a range finding sensor on a motor so a robot could see in every direction. 

I think I may try to build a 360 degree range finder, but I wanted to open this as a topic and get some ideas. Here's what I'm planning. Let me know what you think.


Clock movement as lightweight gearbox

Anyone ever try to modify one of those cheap battery operated analog clock mechanisms as gear train?  It would make an extremely lightweight gearbox for small bot.

Some quick research on the web provided some insight on how these things work:


Then I tore open a broken clockwork that's been sitting around for ages. OK, I tore it open first, then did the research. ; j